Format drifted files to satisfy the treefmt flake-check gate

Pure formatting (nixfmt/prettier/yamlfmt); no behavior change. These
files predate the current treefmt config and were failing nix flake
check; reformatting them makes the gate green again.

modules/mesh-hosts.nix

@@ -11,8 +11,7 @@ let
   dir = config.clan.core.settings.directory;
 
   readVar =
-    machine: file:
-    builtins.readFile "${dir}/vars/per-machine/${machine}/zerotier/${file}/value";
+    machine: file: builtins.readFile "${dir}/vars/per-machine/${machine}/zerotier/${file}/value";
 
   hosts = lib.genAttrs [ "control" "ns1" "ns2" "mx1" ] (m: readVar m "zerotier-ip");